This invention relates to electrical leads, and more particularly to a lead which connects a source of electrical signals to an organ of the body such as the heart.
It is known to stimulate internal body organs such as the heart with electrical signals generated by an electronic device such as a pacemaker. These signals compensate for various cardiac dysfunctions such as rhythm disorders. Generally, the pacing device itself is located some distance away from the organ needing stimulation and is connected to the organ by an electrical lead.
One way of establishing electrode contact with heart muscle is to feed the electrode and its lead through the venous system into the heart. It is necessary in this case that the lead have sufficient stiffness and maneuverability to negotiate the various turns encountered in the journey through the venous system to the heart. It is also desirable that a stimulating lead have small diameter for ease of introduction into the vascular system and also for the ready accommodation of multiple lead systems. In the prior art, it is known to employ a lead with a central hole or lumen. A relatively stiff stylet is inserted into the lumen as an aid for feeding the lead through the venous system. That such prior art leads had a central lumen created by spirally winding the lead conductor around a mandrel which in turn caused the overall lead diameter to be larger than would have been the case without the stylet-receiving lumen. It is known also in the prior art to surround a lead with a stiffening external sheath so as to eliminate a diameter-increasing lumen. These known attempts using an external sheath, however, have not been acceptable because they also required a relatively large diameter. In addition, appropriate stiffness was difficult to achieve and the sheath often kinked because of the sharp bending required to reach a desired location within the heart.
The electrodes on the distal ends of prior art stimulating leads often comprise a cylindrical body having protruding fins for attachment to the organ needing stimulation. These prior art electrodes were of relatively large diameter requiring a large inside diameter introducer for entry into the vascular system.
It is, therefore, an object of the present invention to provide a stimulating lead which has a small diameter resulting from the elimination of the central stylet-receiving lumen.
It is a further object of the present invention to provide a lead having a distal tip of small diameter.
It is yet another object of this invention to provide a lead which is not only very small in diameter but also is extremely rugged and capable of long operating life.